Method and structure for alignment of lens to optical product at pcba level

ABSTRACT

An optical package includes: a Printed Circuit Board including a plurality of cut-out sections; a lens, including a first plurality of protrusions corresponding respectively to the plurality of cut-out sections, wherein when the lens is placed under the PCB, the protrusions will pass through the cut-out sections; and a sensor for attaching on to the lens and the PCB. The first plurality of protrusions has a shape from the group including: snap features, guide posts and guide posts with tight-fit ribs.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention is directed to optical sensor packages, and particularly,to a design and method which can locate, align and lock the position ofa lens and sensor of an optical sensor package at a Printed CircuitBoard Array (PCBA) level.

2. Description of the Prior Art

Optical sensor packages are formed of a sensor and an LED disposed on aprinted circuit board (PCB), which is placed on a base plate comprisinga lens. In order to fix all these components so that the entire packageis stable, the lens is placed in a pocket of the base plate, and isfurther aligned with the optical sensor via a protrusion on the sensorcorresponding to a pocket/depression on the lens. The PCB is presseddown onto the base plate, thus setting the height of the optical sensorpackage.

Refer to FIG. 1 which is a diagram of a prior art optical sensor package100, illustrating the stages of forming the product as well as how theindividual elements are fixed in place.

As shown in the bottom of the diagram, the base plate 110 has a pocketwhich aligns to the shape of the lens 120 for fixing it in place. ThePCB 130 has a cut-out section which corresponds to the entire area ofthe lens 120, and allows the lens 120 to protrude through the PCB 130. Achip (sensor) 140 is placed onto the lens 120 via the cut-out section ofthe PCB 130, wherein the sensor 140 includes a protrusion (notillustrated) which corresponds to a depression/pocket on the lens 120,as illustrated by the circular hole. Finally, an LED 150 and LED clip160 are placed onto the PCB 130 next to the sensor 140. The PCB 130 hasa number of holes for affixing these components.

The structure illustrated in FIG. 1 has some stability issues. Asdescribed above, the lens 120 and the base plate 110 are aligned witheach other, and the lens 120 is aligned with the sensor 140; however,the lens 120 is not aligned with the PCB 130. This means that the lens120 may rotate in a horizontal direction, due to the size of the openingin the PCB 130.

It is therefore an objective of the present invention to provide astructure which improves the stability issues present in the relatedart.

SUMMARY OF THE INVENTION

This in mind, the invention provides a design and method for aligning alens to an optical sensor package at a PCBA level.

An optical package comprises: a Printed Circuit Board (PCB) comprising aplurality of cut-out sections; a lens, comprising a first plurality ofprotrusions corresponding respectively to the plurality of cut-outsections, wherein when the lens is placed under the PCB, the firstplurality of protrusions will pass through the cut-out sections; and asensor for attaching on to the lens and the PCB.

The first plurality of protrusions comprises at least two protrusions,wherein a first protrusion of the first plurality of protrusions isformed on a first side of the lens, and a second protrusion of the firstplurality of protrusions is formed on a second side of the lens oppositeto the first side. The at least two protrusions are of a same shape orare of a different shapes from each other.

In an embodiment, the first plurality of protrusions further comprises athird protrusion having a same shape as the at least two protrusions, ora third protrusion having a different shape from the at least twoprotrusions. The first plurality of protrusions has a shape from thegroup comprising: snap features, guideposts and guide posts withtight-fit ribs.

When at least one of the first plurality of protrusions is guide posts,the guideposts are heat staked or glued to the PCB. The guide posts areglued to the PCB using an epoxy. When at least one of the firstplurality of protrusions is snap features, the snap features compriseinward-facing protrusions which attach to the top of the sensor orcomprise outward-facing protrusions which attach to the PCB.

The lens further comprises a second protrusion and the sensor has afirst feature, wherein the second protrusion is designed to correspondto the first feature for fixing the lens to the sensor. The secondprotrusion is cylindrical and corresponds to a shape of the lens.

A method for designing an optical package is also provided, andcomprises: forming a lens comprising a first plurality of protrusions;forming a Printed Circuit Board (PCB) comprising a plurality of cut-outsections corresponding respectively to the first plurality ofprotrusions; placing the lens under the PCB so that the first pluralityof protrusions pass through the plurality of cut-out sections; andattaching a sensor on to the lens and the PCB.

The first plurality of protrusions comprises at least two protrusions. Afirst protrusion of the first plurality of protrusions is formed on afirst side of the lens, and a second protrusion of the first pluralityof protrusions is formed on a second side of the lens opposite to thefirst side. The at least two protrusions are of a same shape or are of adifferent shape from each other.

The first plurality of protrusions further comprises a third protrusionhaving a same shape as the at least two protrusions or a different shapefrom the at least two protrusions, and the first plurality ofprotrusions has a shape from the group comprising: snap features, guideposts and guide posts with tight-fit ribs.

When at least one of the first plurality of protrusions is guide posts,the method further comprises heat-staking or gluing the guide posts tothe PCB. The guide posts are glued to the PCB using epoxy. When at leastone of the first plurality of protrusions is snap features, the snapfeatures comprise inward-facing protrusions which attach to the top ofthe sensor, or comprise outward-facing protrusions which attach to thePCB.

The step of forming a lens comprising a first plurality of protrusionsfurther comprises: forming a second protrusion on the lens; and the stepof attaching a sensor on to the lens and the PCB further comprises:forming a first feature on the sensor; and attaching the sensor on tothe lens so that the second protrusion corresponds to the first feature.The second protrusion is cylindrical and corresponds to a shape of thelens.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an optical sensor package according to therelated art.

FIG. 2 is a cross-section of an optical sensor package according to anexemplary embodiment of the present invention.

FIG. 3 is a top-view diagram of an optical sensor package according toan exemplary embodiment of the present invention.

FIG. 4A is an assembly view diagram of a lens, sensor and PCB accordingto a first embodiment of the present invention.

FIG. 4B is an exploded view of the lens, sensor and PCB shown in FIG.4A.

FIG. 5A is an assembly view diagram of a lens, sensor and PCB accordingto a second embodiment of the present invention.

FIG. 5B is an exploded view of the lens, sensor and PCB shown in FIG.5A.

FIG. 6A is an assembly view diagram of a lens, sensor and PCB accordingto a third embodiment of the present invention.

FIG. 6B is an exploded view of the lens, sensor and PCB shown in FIG.6A.

FIG. 7A is an assembly view diagram of a lens, sensor and PCB accordingto a fourth embodiment of the present invention.

FIG. 7B is an exploded view of the lens, sensor and PCB shown in FIG.7A.

DETAILED DESCRIPTION

The present invention provides a design for an optical sensor package ata PCBA level, wherein a lens can be aligned to both a PCB and to asensor of the optical sensor package. This provides greater stability inboth a vertical and horizontal direction.

Refer to FIG. 2 , which is a side-on diagram of part of an opticalsensor package 200 according to an embodiment of the present invention.Note that this diagram does not illustrate a base plate, but merelyshows a PCB 230, lens 220, LED 250 and sensor package 240. Two specificfeatures are highlighted in the diagram: Feature A and Feature B.

Feature A is for attaching the lens 220 to the sensor package 240, andcomprises a cylindrical surface corresponding to the concentric surfaceof the lens 220. The fitting must be tight or have minimal clearance inorder to ensure optimum optical performance. As the surface of Feature Ais rounded, there is still the possibility of rotation of the lens 220with respect to the sensor package 240.

Feature B is for locking the lens 220 into place with respect to the PCB230, which can ensure stability in both a vertical direction and ahorizontal (rotational) direction. Moreover, by enabling the lens 220 tobe locked into place with respect to both the sensor 240 and the PCB230, the lens 220, sensor 240 and PCB 230 form a stable component thatcan then be fixed onto the base plate (not illustrated) as a singlepiece, which makes assembly easier.

Refer to FIG. 3 which is a top-view diagram of an optical sensor package300 according to an exemplary embodiment of the present invention. Asshown in the diagram, Feature B comprises three separate features.Further, in this embodiment, the two features on the left-hand side ofthe PCB 230 have a different shape from the single feature on theright-hand side of the PCB 230. It should be noted that the invention isnot limited to the number and shape of Feature B as shown in FIG. 3 . Inpractice, Feature B may comprise a single feature, two features, threefeatures etc. The number of features is only limited by the size of thePCB, as there will be a tradeoff between stability and area. Further, nomatter how many features comprises Feature B, they may all have the sameshape, they may all have different shapes or they may have thedistribution as shown in FIG. 3 . In a preferred embodiment, Feature Bcomprises at least two features placed on either side of the sensor 240,so that the optical sensor package can be locked in the horizontal(rotational) direction. The choice of shapes and numbers will depend onpractical requirements such as cost, stability and ease ofmanufacturing.

The following diagrams illustrate different embodiments of Feature B.For ease of illustration, in each embodiment illustrated herein, FeatureB comprises three individual features which are all the same shape.

Refer to FIG. 4A and FIG. 4B. FIG. 4A is an assembly view of a lens 220,sensor 240 and PCB 230 according to a first embodiment of the invention.For ease of description, the lens 220, sensor 240 and PCB 230 willherein be referred to as a sensor package 400. FIG. 4B is an explodedview of the sensor package 400 shown in FIG. 4A. In this embodiment,Feature B consists of three snap features. The snap features will snaponto the sensor package 400, thereby locking the lens 220 to the sensor240 in the Z-direction. As shown in FIG. 4B, the PCB 230 has cut-outsections which are for guiding the snap features.

In this embodiment, the snap features have protrusions facing inwardsfor locking onto the sensor 240. The snap features therefore need to betall enough to clear the sensor 240 and lock onto the top of the sensor240.

A sensor package 500 according to a second embodiment of the inventionis shown in FIG. 5A and FIG. 5B. In this embodiment, Feature B comprisessnap features but they are for locking onto the PCB 230 rather than ontothe sensor 240. The snap features/protrusions of Feature B faceoutwards, so they do not interfere with the sensor 240. By locking ontothe PCB 230 rather than the sensor 240, the snap features can be shorterthan in the first embodiment 400. This provides a more rigid structure.Due to Feature A, the position of the lens 220 with respect to thesensor 240 is stable.

A sensor package 600 according to a third embodiment of the inventionuses guide posts, as illustrated in FIG. 6A and FIG. 6B. Rather thansnapping onto the PCB 230 or sensor 240, the guide posts are glued orheat staked to the PCB 230. A disadvantage of gluing the guide posts isthat excess glue/epoxy may be left on the PCB 230, as the epoxy can bemessy and hard to control. Heat stake posts do not have this issue, butthey do require an extra step in the assembly process for heating theposts to fix them to the PCB 230.

A sensor package 700 according to a fourth embodiment of the inventionuses guide posts with tight-fit ribs, as shown in FIG. 7A and FIG. 7B.As in FIG. 6A, the guide posts pass through the cut-out sections of thePCB 230. In contrast with the embodiment shown in FIG. 6A and FIG. 6B,however, the tight-fit ribs on the guide posts (illustrated by thedarker features) allow the guide posts to lock the PCB 230 to the lens220 without requiring gluing or heat-staking.

By designing a lens to include features allowing it to be aligned to aPCB as well as to a sensor, the lens not only can be fixed into a stableposition with respect to the height of the structure (Z position), butalso ensure that the lens will not rotate in the horizontal direction.

The lens can be designed in one piece, including the Feature A andFeatures B. The PCB should be designed to follow the design of the lens,as cut-out sections in the PCB are needed for guiding and locatingFeatures B. When Feature B comprises guide posts, the assembly willrequire an extra step for heat-staking the guide posts to the PCB.

By locking all components of the optical sensor package in alldirections (x, y, z), the overall system tolerance is reduced, and arobust package can be created which can improve optical tracking.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optical package, comprising: a Printed CircuitBoard (PCB) comprising a plurality of cut-out sections; a lens,comprising a first plurality of protrusions corresponding respectivelyto the plurality of cut-out sections, wherein when the lens is placedunder the PCB, the first plurality of protrusions will pass through thecut-out sections; and a sensor for attaching on to the lens and the PCB.2. The optical package of claim 1, wherein the first plurality ofprotrusions comprises at least two protrusions.
 3. The optical packageof claim 2, wherein a first protrusion of the first plurality ofprotrusions is formed on a first side of the lens, and a secondprotrusion of the first plurality of protrusions is formed on a secondside of the lens opposite to the first side.
 4. The optical package ofclaim 2, wherein the at least two protrusions are of a same shape. 5.The optical package of claim 2, wherein the at least two protrusions areof a different shape from each other.
 6. The optical package of claim 4,wherein the first plurality of protrusions further comprises a thirdprotrusion having a same shape as the at least two protrusions.
 7. Theoptical package of claim 4, wherein the first plurality of protrusionsfurther comprises a third protrusion having a different shape from theat least two protrusions.
 8. The optical package of claim 7, wherein thefirst plurality of protrusions has a shape from the group comprising:snap features, guide posts and guide posts with tight-fit ribs.
 9. Theoptical package of claim 8, wherein at least one of the first pluralityof protrusions is guide posts, and the guide posts are heat staked tothe PCB.
 10. The optical package of claim 8, wherein at least one of thefirst plurality of protrusions is guide posts, and the guide posts areglued to the PCB.
 11. The optical package of claim 10, wherein the guideposts are glued to the PCB using an epoxy.
 12. The optical package ofclaim 8, wherein at least one of the first plurality of protrusions issnap features, and the snap features comprise inward-facing protrusionswhich attach to the top of the sensor.
 13. The optical package of claim8, wherein at least one of the first plurality of protrusions is snapfeatures, and the snap features comprise outward-facing protrusionswhich attach to the PCB.
 14. The optical package of claim 1, wherein thelens further comprises a second protrusion and the sensor has a firstfeature, wherein the second protrusion is designed to correspond to thefirst feature for fixing the lens to the sensor.
 15. The optical packageof claim 14, wherein the second protrusion is cylindrical andcorresponds to a shape of the lens.
 16. A method for designing anoptical package, comprising: forming a lens comprising a first pluralityof protrusions; forming a Printed Circuit Board (PCB) comprising aplurality of cut-out sections corresponding respectively to the firstplurality of protrusions; placing the lens under the PCB so that thefirst plurality of protrusions pass through the plurality of cut-outsections; and attaching a sensor on to the lens and the PCB.
 17. Themethod of claim 16, wherein the first plurality of protrusions comprisesat least two protrusions.
 18. The method of claim 17, wherein a firstprotrusion of the first plurality of protrusions is formed on a firstside of the lens, and a second protrusion of the first plurality ofprotrusions is formed on a second side of the lens opposite to the firstside.
 19. The method of claim 17, wherein the at least two protrusionsare of a same shape.
 20. The method of claim 17, wherein the at leasttwo protrusions are of a different shape from each other.
 21. The methodof claim 19, wherein the first plurality of protrusions furthercomprises a third protrusion having a same shape as the at least twoprotrusions.
 22. The method of claim 19, wherein the first plurality ofprotrusions further comprises a third protrusion having a differentshape from the at least two protrusions.
 23. The method of claim 22,wherein the first plurality of protrusions has shapes from the groupcomprising: snap features, guide posts and guide posts with tight-fitribs.
 24. The optical package of claim 23, wherein at least one of thefirst plurality of protrusions is guide posts, and the method furthercomprises: heat-staking the guide posts to the PCB.
 25. The opticalpackage of claim 23, wherein at least one of the first plurality ofprotrusions is guide posts, and the method further comprises: gluing theguide posts to the PCB.
 26. The optical package of claim 25, wherein theguide posts are glued to the PCB using an epoxy.
 27. The optical packageof claim 23, wherein at least one of the first plurality of protrusionsis snap features, and the snap features comprise inward-facingprotrusions which attach to the top of the sensor.
 28. The opticalpackage of claim 23, wherein at least one of the first plurality ofprotrusions is snap features, and the snap features compriseoutward-facing protrusions which attach to the PCB.
 29. The method ofclaim 16, wherein the step of forming a lens comprising a firstplurality of protrusions further comprises: forming a second protrusionon the lens; and the step of attaching a sensor on to the lens and thePCB further comprises: forming a first feature on the sensor; andattaching the sensor on to the lens so that the second protrusioncorresponds to the first feature.
 30. The method of claim 29, whereinthe second protrusion is cylindrical and corresponds to a shape of thelens.